At that, one of the seraphs flew to me, and in his hand there was a glowing coal that he had taken with tongs off the altar. And he proceeded to touch my mouth and to say: ‘Look! This has touched your lips, and your error has departed and your sin itself is atoned for.’”​—Isa 6:1-7.

One of the seraphs touched Isaiah’s lips to cleanse away his sin and his error by means of a glowing coal from off the altar. This may indicate that their work is in some way associated with cleansing away sin from among God’s people, such cleansing being based on the sacrifice of Jesus Christ on God’s altar.​—Isa 6:3, 6, 7.